It is known to store and transport nuclear waste by having the nuclear material immobilized by being a component of a synthetic “rock” or glass-ceramic matrix. The rock matrix being located in a metal canister. As one example, the rock matrix is formed by mixing the nuclear material in powdered form, with a powered metal, such as copper. However, in this regard other materials can be used, such as a ceramic or glass or mixed glass-ceramic powder. The resulting rock matrix is highly resistant to corrosion and retains the waste in an immobilized form. The canisters are also formed from a material that is highly resistant to corrosion, such as stainless steel.
In one example the canister is of a generally cylindrical configuration with the longitudinal cylindrical wall being of a convoluted bellows or second example an “hour glass” (dumb-bell) configuration. Prior to the canister being hermetically sealed, gas is evacuated therefrom so that the canister has a lowered internal pressure relative to its surroundings. Thereafter the canister is subjected to a hot isostatic pressing process in which the temperature of the canister and its contents is raised (typically to a temperature up to 1400° C.) for a period of two to four hours at a pressure up to 400 MPA. Due to the corrugated side wall of the canister and the softening of the metal at high temperature, the pressure is transferred to the powder which results in the formation of the abovementioned dense matrix.
Examples of the abovementioned canisters and process are described in U.S. Pat. Nos. 4,834,917 and 4,808,337. In U.S. Pat. No. 4,834,917 a container is described in which an inner canister is located within an outer canister prior to being inserted in the furnace.
A disadvantage of the above described method is that should the canister not be totally hermetically sealed, then damage to the furnace can result. If the canister leaks, gas from within the furnace will enter the canister with the result, that when the environment within the furnace is lowered to ambient pressure, the canister will deform by expanding longitudinally and/or may rupture. This is a disadvantage in that damage to the furnace, in particularly the furnace wall may result. This may be mechanical damage and/or contamination with nuclear material.